The p53 transcription factor has been considered one of the most appealing targets for developing anticancer treatments. Indeed, the fact that the p53-signaling pathway is inactivated in all types of cancers has drawn great attention from the world-wide cancer researchers to target p53 for the development of improved cancer therapies. Specifically, about 50% of the patients contain various inactivating mutations in p53, while the other 50% possess defective components in posttranslational modification of the p53 protein or abrogation of the p53-signaling pathway by endogenous negative regulators, such as MDM2 and MDMX. The transformed environment of tumor cells appears to be super-responsive to the re-introduction of p53 activity, which turns on the tumor suicidal pathway. Based on this, several small-molecules targeting the p53 pathway have emerged, most of them targeting the p53 interaction with MDM2.
The high prevalence of mutant forms of p53 in human cancers and the often observed increased drug resistance of mutant p53-expressing tumors makes mutant p53 forms highly appealing targets for novel cancer therapies. Additionally, due to its high selectivity for tumor cells, by reactivating the mutant p53, high efficiency combined with minimum side effects can be achieved. Even though the diversity of mutations in tumors, the majority have common features that would make restoring wild-type p53 functions feasible. Most of them are missense mutations in the DNA-binding core domain that results in mutant p53 conformational changes and consequent loss of DNA binding activity. Hence, the search for small-molecules that can stabilize mutant p53 in its active biological conformation by restoring its binding and transcriptional activity will have a profound impact on cancer therapy. Recently, this approach led to the identification of some small-molecules that restore wild-type p53 function to a wide range of p53 mutants (e.g. CP-31398 and PRIMA-1).
Despite the recent identification of some p53 activators, for most of them, the molecular mechanism of action is far from being clear. Additionally, the few described compounds might have unfavorable pharmacokinetics or toxicity profiles and therefore will not be useful. Thus, more potent and selective pharmacological alternatives to the activation of p53 function for neoplastic cells are still largely required, specially avoiding deleterious adverse effects associated with many of the current cancer therapies [reviewed in (Wade et al. Nat. Rev. Cancer 2013, 13, 83-96; Pei et al., Oncotarget 2012, 3, 228-235; Chen et al. Biochem Pharmacol. 2010, 80:724-30; Wiman 2010 Oncogene 29:4245-52; Wang and Sun, Translational Oncology 2010, 3:1-12)].